Field of the Invention
The present invention relates to an aqueous ink, an ink cartridge, and an ink jet recording method.
Description of the Related Art
In recent years, inks containing pigments (pigment inks) as coloring materials have been widely used as an ink used for an ink jet recording method. In order to give glossy images such as photographs, an ink containing a resin-dispersed pigment in which a pigment is dispersed by a resin (resin dispersant) is typically used. If the ink containing the resin-dispersed pigment is used, highly tough images can be recorded because the pigment is present in the form of particles in the ink. However, the images recorded with the pigment inks unfortunately have lower gloss clarity than those of images recorded with dye inks in which dyes are dissolved in an aqueous medium. The “gloss clarity” is an indicator of the characteristics commonly used for evaluating glossy images and an indicator of clearness and distinctness of an image recorded on the surface of a recording medium.
To solve that problem, various techniques have been disclosed. In one of the techniques, a silicone-containing surfactant or a fluorinated surfactant is added to lower the surface tension of an ink, and thus the wettability and the permeability of the ink with respect to a recording medium is improved. For example, an ink containing a silicone-containing surfactant or a fluorinated surfactant (Japanese Patent Application Laid-Open No. 2012-184376) and an ink that is so adjusted that the surface tension before evaporation is larger than the surface tension after evaporation (Japanese Patent Application Laid-Open No. 2012-224658) have been disclosed. Moreover, an ink in which the change in dynamic surface tension of the ink is specified has been disclosed (Japanese Patent Application Laid-Open No. 2014-025055). In addition, an ink containing a fluorinated surfactant and a foam suppressor has been disclosed (Japanese Patent Application Laid-Open No. 2010-275377).
The result of the study by the inventors of the present invention, however, has revealed that when the ink disclosed in Japanese Patent Application Laid-Open No. 2012-184376, Japanese Patent Application Laid-Open No. 2012-224658, or Japanese Patent Application Laid-Open No. 2014-025055 is used to record images on recording mediums such as glossy paper, the gloss clarity of images may be improved depending on the constitution of inks, but the gloss clarity of images deteriorates in many cases. The result has also revealed that even when the ink capable of improving the gloss clarity of images is used, the difference in gloss is large between a high density area and a low density area (i.e., gloss unevenness is conspicuous). In other words, with regard to the improvement of gloss clarity and the suppression of gloss unevenness, images satisfying recently demanded high quality cannot be recorded. The ink disclosed in Japanese Patent Application Laid-Open No. 2010-275377 gives conspicuous gloss unevenness and cannot produce satisfactory images.
An object of the present invention is to provide an aqueous ink capable of performing recording of images having excellent gloss clarity and small gloss unevenness. Another object of the present invention is to provide an ink cartridge and an ink jet recording method using the aqueous ink.